An optical transmission circuit comprises an optical fiber cable received in protective tubes that are connected to one another by connection devices. The installation of such a circuit begins by laying and connecting together tubes in which the optical fiber cable is to be inserted using air pressure so that the cable is pushed along the tubes by the air. The connection devices therefore need to present two states: an insertion state in which the optical fiber cable is allowed to pass freely, and a utilization state in which the connection devices isolate the tubes they connect together by leaktight sealing around the optical fiber cable.
Document US-A-2007/200344 discloses a device for connecting together optical fiber cable protection tubes, the device comprising a tubular body defining a channel having a first end housing and a second end housing, each of which housings is arranged to receive one of the tubes and is provided with means for retaining said tubes in sealed manner. The bodies include an annular step extending between the housings so as to form an abutment against penetration of the tubes into the housings. An annular sealing element is arranged in the first housing in the vicinity of a frustoconical flank of the step. The sealing element has a rest state in which the sealing element defines a free section through which the cable can pass. While the tube is being pushed into the first housing, the tube forces the sealing element into the constriction defined inside the channel by the annular step, thereby deforming the sealing element into a second state in which the sealing element defines a section that is less than the section of the cable. Forced engagement of the sealing element into the constriction of the channel requires the user to apply significant force while inserting the tube into the first housing. In addition, the sealing element behaves randomly while it is being engaged in the constriction. That makes it difficult for the operator to determine whether the tube has been pushed in sufficiently to obtain the desired deformation of the sealing element. It is difficult to dimension the sealing element and the constriction in the channel, and it is also difficult to select the material for the sealing element. Finally, those connections are not reusable, since the sealing element remains in its second state after the tubes have been withdrawn.